The faces command monitors incoming mail and displays in its window
a representation of the user's mail box using a small image for
each message. The image is typically a portrait of the sender.
Which image to display is determined by two directories /usr/$user/lib/face
and /lib/face. Entries in /usr/$user/lib/face
take priority over those in /lib/face. See face(6), for how these
directories are organised.

If the user is running plumber(4), faces reacts to plumb messages
to the seemail port, typically from upas/fs, and is thus notified
of message additions and deletions.

Right–clicking on a message icon causes that message to be `plumbed'
to showmail. A typical plumb action will be to display the message,
such as by the rule

If the user is not running plumber, faces reads the log file and
right–clicking has no effect.

If arrows are visible, clicking on them will scroll the display.
Middle–clicking on the arrows scrolls to the end.

Starting faces with the –i flag causes faces to read the messages
in /mail/fs/mbox — or the mailboxes specified with the –m flag
— upon startup.

The –m option directs faces to watch for messages arriving in maildir
instead of /mail/fs/mbox. Multiple –m flags may be used to watch
multiple mailboxes.

The –h flag causes a different, venerable behavior in which the
window displays the history of messages received rather than the
current state of the mail box. In particular, faces are not removed
from the screen when messages are deleted. Also, in this mode
clicking button 1 in the display will clear the window.